Fire damper

ABSTRACT

A fire damper having blades restricted to less than 180 degrees relative articulation for added strength and ease in reopening after the damper has been closed. A foldable blade assembly is disposed in a supporting framework. Each blade of the blade assembly has an intermediate portion with incomplete generally cylindrical end portions at either side of the intermediate portion. The cylindrical end portions are of different sizes so that one end portion can fit inside of another end portion on an adjacent blade. Each of the generally cylindrical portions terminates in a radially extending lip. Adjacent blades are disposed with the cylindrical portions facing each other so as to unfold in a serpentine configuration. As the blades unfold the cylindrical portion of one blade turns inside the cylindrical portion of an adjacent blade until the two radially extending lips interengage to positively lock and prevent further opening. Optimum operating results are obtained when the relative articulation between adjacent blades is no more than 140*. A novel catch is employed in some instances to positively lock the blades in their unfolded position. In cooperation with a spring positioned to urge the blades toward their unfolded positions the catch positively locks the blades once they have unfolded.

United States Patent Root [451 Sept. 23, 1975 FIRE DAMPER [75] Inventor: James R. Root, Independence, Mo.

[73] Assignee: Ruskin Manufacturing Company, Grandview, Mo.

[22] Filed: July 12, 1973 [21] Appl. No.: 378,511

Primary Examiner-Philip C. Kannan Attorney, Agent, or FirmLowe, Kokjer, Kircher, Wharton & Bowman [57] ABSTRACT A fire damper having blades restricted to less than 180 degrees relative articulation for added strength and ease in reopening after the damper has been closed. A foldable blade assembly is disposed in a supporting framework. Each blade of the blade assembly has an intermediate portion with incomplete generally cylindrical end portions at either side of the intermediate portion. The cylindrical end portions are of different sizes so that one end portion can fit inside of another end portion on an adjacent blade. Each of the generally cylindrical portions terminates in a radially extending lip. Adjacent blades are disposed with the cylindrical portions facing each other so as to unfold in a serpentine configuration. As the blades unfold the cylindrical portion of one blade turns inside the cylindrical portion of an adjacent blade until the two radially extending lips interengage to positively lock and prevent further opening. Optimum operating results are obtained when the relative articulation between adjacent blades is no more than: 140. A novel catch is employed in some instances to positively lock the blades in their unfolded position. In cooperation with a spring positioned to urge the blades toward their un folded positions the catch positively locks the blades once they have unfolded.

3 Claims, 6 Drawing Figures US Patent Sept. 23,1975 Sheet 2 of2 3,907,020

FIRE DAMPER This invention relates to closures for air ducts and, more particularly to a folding blade closure for use as a fire damper.

Closures of this type conventionally comprise an assembly of hingedly interconnected blades which are normally disposed in a folded, stand-by position adjacent one side of a rigid framework. The closure is disposed in an air duct or the like for closing the duct in the event of a fire. The assembly is normally held in its stand-by position by a destructible device such as a fusible link so as to assure automatic operation under appropriate conditions.

In some instances a fire damper closure of the type described is mounted vertically across a generally horizontally extending duct or passage and gravity is relied upon for unfolding the blades of the assembly after release of the fusible link or other locking device. When, however, the unit is required to be installed in a horizontal position as is necessary for protecting a generally vertically extending shaft, an auxiliary spring is normally necessary to assure positive movement of the blade assembly across the frame opening upon destruction of the fusible link.

In recent years, one of the improvements in the field of fire dampers has been to utilize a blade assembly held in a stand-by position by an energized motor. This allows for the blade assembly to be closed to block off an air passage by interrupting the supply of electrical energy to the motor. Thus, in many instances where smoke would flow through a passage because the tem perature does not reach a sufficient level to destruct even the most sensitive fusible link, fire control is accomplished by the electrically operated damper. The use of such dampers has made it even more imperative, however. that the blades of the blade assembly can be easily returned to their folded position once the need to block the air duct has terminated.

Folded blade assemblies utilized in smoke and fire dampers of the prior art have largely employed blades which could articulate relative to each other approximately 180 as they moved from a folded to an unfolded position. While it has previously been recognized that a blade assembly wherein the blades rotated relative to each other less than 180 could offer advantages in strength and ease of resetting the blades to a folded position, efforts to construct such a damper have heretofore met with several problems.

One of the disadvantages of foldable blade assem blies where the blades are prevented from opening a full 180 has been that the limited opening of the blades has resulted in a spring action" which does not assure a positive closing. Another disadvantage of prior art constructions wherein attempts have been made to limit the degree of opening of the blades has been the reliance upon two adjacent blades biasing or binding as they intcrengage to limit their relative movement. This is, inherently, an undesirable means of limiting the blade opening because of the tendency to get a spring action and difficulty in returning the blades to a folded position. Still another disadvantage of prior art constructions wherein limited blade openings have been attempted is their susceptibility to becoming completely disengaged upon application of substantial heat in the event of a fire in close proximity to the damper.

It is therefore an object of the present invention to provide a fire damper employing a foldable blade assembly wherein the blades have relative movement of less than 180 and wherein spring action of the blades upon opening is eliminated by interconnecting the blades in a manner so as to present a positive stop to limit the degree of opening.

Another object of this invention is to provide a fire damper with a limited blade articulation wherein any spring action of the blades upon opening as well as the tendency of the blades to become unwrapped from one another upon the application of substantial heat is avoided by avoiding the dependency upon two adjacent blades biasing each other to limit their opening.

An important aim of this invention is also to provide a catch construction for a fire damper intended to be disposed in a substantially horizontal position wherein the catch positively locks the endmost blade of the assembly through use of a camming action.

A further objective of the invention is to provide a catch as described in the foregoing object which requires no holes or other modifications to be made in the end blade of the assembly.

It is also an aim of the invention to provide a catch for a foldable fire damper blade assembly which positively locks the blades in an unfolded position and yet can be readily opened from either side of the blade assembly as a result of a camming action which pivots the endmost blade around a camming surface to unlock it in the same manner as locking is achieved when the force is applied in the opposite direction.

Other objects of the invention will be made clear or become apparent from the following descriptions when read in light of the accompanying drawing and claims.

In the drawing:

FIG. 1 is a perspective view of a fire damper con structed according to the present invention with the blade assembly disposed in a folded position;

FIG. 2 is an enlarged vertical cross-sectional view through the damper shown in FIG. 1 and illustrating in detail the blade assembly as the latter is disposed in its folded position;

FIG. 3 is an enlarged fragmentary side elevational view of the catch construction disposed at one end of the damper framework and which positively locks the endmost blade of the blade assembly;

FIG. 4 is another fragmentary elevational view, similar to FIG. 3, and illustrating the position of the endmost blade immediately prior to being locked in the catch structure;

FIG. 5 is a second vertical crosssectional view. similar to FIG. 2, and illustrating the unfolded position of the blades with the endmost blade securely locked by the catch structure; and

FIG. 6 is a greatly enlarged, vertical cross-sectional view of two adjacent blades of the assembly illustrating how the blades positively interlock to limit the degree of articulation between them.

Referring initially to FIG. 1, the fire damper of the present invention is designated generally by the numeral 10. A framework 12 is :normally formed from a flat material such as sheet metal or the like and is bent into a generally rectangular configuration to present opposed sidewalls l4 and end walls 16. The terminal edges of each of the walls 14 and 16 are bent back upon themselves to form stiffening ribs at the edges and then turned outwardly at degrees to the wall to present channel defining edges 18. Framework 12 is adapted to be disposed in an air duct or other fluid passage of a structure with the opening defined by framework 12 normally permitting air flow through the damper.

A blade assembly 20 (FIG. 2) is comprised of a number of individual interconnected blades 22. Assembly 20 is secured to framework 12 by rivets 24 passing through the upper endwall 16 and the first blade 22 of the assembly.

Each blade 22 of the assembly is identical and only one blade will therefore be described in detail with particular reference to FIGS. and 6. Each blade 22 comprises a generally planar intermediate portion 26 which spans the distance between opposed sidewalls 14. Integral with intermediate portion 26 is a first incomplete generally cylindrical portion 28 which terminates in an integral planar lip 30. Lip 30 extends generally radially inwardly from the line of curvature of first cylindrical portion 28 in generally perpendicular relationship to an imaginary tangent at the terminal point of the cylindrical portion. The arcuate stretch connecting lip 30 with the curvilinear section of portion 28 forms a heel 31 along the outer periphery as the cylindrical portion merges into lip 30 (FIG. 6).

At the opposite edge of intermediate portion 26 from first cylindrical portion 28 is a second incomplete generally cylindrical portion 32 of a slightly smaller radius of curvature than first portion 28. Second cylindrical portion 32 also has an integral planar lip 34. Lip 34 extends generally radially inwardly from the line of curvature of portion 32 and generally perpendicular to an imaginary tangent at the terminal point of the second cylindrical portion.

Manifestly, blades 22 are disposed with adjacent cylindrical portions 28 and 32 facing each other so that the smaller portion 32 can turn within the larger portion 28. The blades are normally held in a folded position at the top of framework 12 by a fusible link 36 mounted by a U-bracket 38.

Mounted at the end of framework 12 opposite the end to which blade assembly 20 is secured are catch components 40 for locking the assembly in its unfolded position. As can be seen from viewing FIG. 1, two components 40 are preferably employed although only one of the same would be described in detail. Each component 40 includes a generally planar upright wall 42 extending from end wall 16 upwardly into the opening presented by the framework. A first blade catch 44 is generally complemental to the first cylindrical portion 28 and is spaced upwardly from a second blade catch 46 which is generally complemental to the second cylindrical portion 32 of the endmost blade of the assembly. Blade catches 44 and 46 are separated by a camming surface 48 disposed to engage intermediate portion 26 of the endmost blade. A first generally arcuate guide surface 50 extends outwardly away from first blade catch 44 in disposition for engagement with the first cylindrical portion to guide the latter into the first catch. Similarly, a second guide surface 52 extends outwardly from second blade catch 46 to guide second cylindrical portion 32 into the second catch.

Each catch component 40 also serves to mount a negator type coiled spring 54 having one end secured to the endmost blade 22 of assembly 20. Thus, spring 54 serves to urge blades 22 to their unfolded position.

In many instances, damper is installed in a generally horizontal duct so that it assumes the upright position as illustrated in FIG. 'li' ln such installations, it is generally not necessary to install catch components 40 and spring 54 since gravitational forces can be relied upon to positively unfold blade assembly 20 upon destruction of link 36. When link 36 is severed by temperatures reaching the design maximum the individual blades 22 will move relative to each other to the unfolded position illustrated in FIG. 5.

Because the number of blades 22 utilized in assembly 20 is greater than the minimum number required to span the distance from one end wall 16 to the other, all of the blades do not move relative to each other to the maximum extent possible. It is to be understood, of course, that in actual production models of damper 10, there will normally be a greater number of blades in assembly 20 than illustrated in the drawings in order to span the distance of a substantially larger opening than the one shown for illustration purposes herein. Thus, there will normally be a number of blades 22 which do move relative to each other to the maximum extent possible as is the case with the second and third uppermost blades of assembly 20 in FIG. 5.

As best illustrated in FIG. 6, the second cylindrical portion 32 of one blade turns within the first cylindrical portion 28 of an adjacent blade until the heel 31 of the first portion 28 engages the inner surface of second portion 32 while lip 30 of first portion 28 engages lip 34 of second portion 32 to interlock and form a positive stop for the two blades. It has been found that optimum operating conditions result when the blades 22 are designed to limit relative movement between adjacent blades to no greater than The resulting serpentine configuration of the unfolded blade assembly results in a substantially stronger damper allowing blades 22 to be constructed of a greater width for intermediate portions 26 than has heretofore been possible. This, in turn, reduces the number of blades required to span an opening of a given size and allows for the assembly to be substantially more compact when in its folded position. In many applications this will eliminate the need for a depending protective skirt from the upper end wall 16 to block the flow of air through the folded blade assembly 20.

It is also inherent in the design of blades 22 that after the assembly has been unfolded and it is desired to return the blades to a folded position, there is virtually no chance of the blades binding in such a way as to interfere with their return to the folded position. This is particularly advantageous where a motor operated return is utilized. Also, because of the positive stop action which interlocks adjacent blades 22 it has been found that there is no spring action upon unfolding of the blades and no tendency for the blades to become unwrapped and unconnected upon the application of high temperatures.

In those instances where damper 10 is installed in a generally vertical duct so that the damper assumes a substantially horizontal position, spring 54 and catch components 40 are utilized to assure positive operation of the damper. Spring 54 continually biases blades 22 toward an unfolded position although so long as fusible link 36 remains intact, this is not possible. Once link 36 has been destroyed because of high temperatures, spring 54 will move the assembly to the unfolded position illustrated in FIG. 5. As illustrated in FIG. 3, spring 54, which is connected to inmost blade 22 at a point off center relative to the intermediate portion 26 moves the endmost blade into engagement with guide surfaces 50 and 52 of catch component 40. Cylindrical portions 28 and 32 travel along the respective guide surfaces until they move into position adjacent their respective catches 44 and 46 as best illustrated in FIG. 4. At this point, intermediate portion 26 engages camming surface 48 and, because of the off center connection of spring 54 with the endmost blade, the latter pivots about the camming surface to move portions 28 and 32 into firm locking engagement with their respective catches as illustrated in FIG. 5. Once in the position shown in FIG. 5, the blade assembly is firmly locked and cannot be opened by the application of any forces such as a stream of water emanating from a fire hose, that might be traveling along the direction of the duct in which damper is disposed.

A particular advantage of the design of catch 40 is, however, that it allows the blade assembly to be returned to its folded position from either side of damper 10. Thus, by applying a force opposite to the direction of force exerted by spring 54 the endmost blade 22 of the assembly again pivots about camming surface 48 to unlock cylindrical portions 28 and 32 from their respective catches. Again, return of the assembly 20 to its folded position without catching of blades 22 is assured because of the limited relative articulation of adjacent blades.

I claim:

1. A fire damper comprising:

a housing defining an opening;

a plurality of interconnected blades coupled with said housing and movable relative to each other from a folded to an unfolded position.

each of said blades comprising a generally planar intermediate portion having at opposite ends first and second incomplete generally cylindrical portions terminating in first and second generally planar lips. respectively,

said first cylindrical portion extending through an arc of approximately 240 and presenting a heel along its outer periphery as it merges into said planar lip and having a larger radius than said second cylindrical portion, the latter extending through an arc of approximately and adapted to turn within said first portion as said blades move relative to each other, Y

said first lip being directed radially inward at an oblique angle relative to an imaginary extension of said planar intermediate portion and being of a length greater than the length of said second lip,

said second lip being directed radially inward in generally planar alignment with said planar intermediate portion,

1 whereby when said blades move to said unfolded position and said second cylindrical portion turns in the first cylindrical portion, the terminal end of said first lip engages the second lip at the point of juncture of the latter with said second cylindrical portion and the heel of said first portion engages the inner surface of said second portion thereby limiting the relative angular movement between adjacent blades to less than 180 and means for holding said blades in a folded position during normal operating conditions and for releasing said blades during fire conditions to block said opening.

2. The invention of claim 1, wherein said structure further comprises a first guide surface extending outwardly away from said first catch in disposition for engagement with said first cylindrical portion to guide the latter into said first catch, and a second guide surface extending outwardly away from said second catch in disposition for engagement with said second cylindrical portion to guide the latter into said second catch.

3. The invention of claim 2, wherein said biasing means comprises a spring secured to said endmost blade at a point on said intermediate portion, said point located to one side of said camming surface whereby when said intermediate portion engages said camming surface said spring pivots said endmost blade about the camming surface to move said first and second cylindrical portions into locking engagement with said first and second catches, respectively. 

1. A fire damper comprising: a housing defining an opening; a plurality of interconnected blades coupled with said housing and movable relative to each other from a folded to an unfolded position, each of said blades comprising a generally planar intermediate portion having at opposite ends first and second incomplete generally cylindrical portions terminating in first and second generally planar lips, respectively, said first cylindrical portion extending through an arc of approximately 240* and presenting a heel along its outer periphery as it merges into said planar lip and having a larger radius than said second cylindrical portion, the latter extending through an arc of approximately 180* and adapted to turn within said first portion as said blades move relative to each other, said first lip being directed radially inward at an oblique angle relative to an imaginary extension of said planar intermediate portion and being of a length greater than the length of said second lip, said second lip being directed radially inward in generally planar alignment with said planar intermediate portion, whereby when said blades move to said unfolded position and said second cylindrical portion turns in the first cylindrical portion, the terminal end of said first lip engages the second lip at the point of juncture of the latter with said second cylindrical portion and the heel of said first portion engages the inner surface of said second portion thereby limiting the relative angular movement between adjacent blades to less than 180* and means for holding said blades in a folded position during normal operating conditions and for releasing said blades during fire conditions to block said opening.
 2. The invention of claim 1, wherein said structure further comprises a first guide surface extending outwardly away from said first catch in disposition for engagement with said first cylindrical portion to guide the latter into said first catch, and a second guide surface extending outwardly away from said second catch in disposition for engagement with said second cylindrical portion to guide the latter into said second catch.
 3. The invention of claim 2, wherein said biasing means comprises a spring secured to said endmost blade at a point on said intermediate portion, said point located to one side of said camming surface whereby when said intermediate portion engages said camming surface said spring pivots said endmost blade about the camming surface to move said first and second cylindrical portions into locking engagement with said first and second catches, respectively. 